Kleshas (Sanskrit, also kleśa; Pali: kilesa; Tibetan: nyon mongs), in Buddhism, are mental states that cloud the mind and manifest in unwholesome actions. Kleshas include states of mind such as anxiety, fear, anger, jealousy, desire, depression, etc. Contemporary translators use a variety of English words to translate the term kleshas, such as: afflictions, defilements, destructive emotions, disturbing emotions, negative emotions, mind poisons, etc.

In the contemporary Mahayana and Theravada Buddhist traditions, the three kleshas of ignorance, attachment, and aversion are identified as the root or source of all other kleshas. These are referred to as the three poisons in the Mahayana tradition, or as the three unwholesome roots in the Theravada tradition.

While the early Buddhist texts of the Pali canon do not specifically enumerate the three root kleshas, over time the three poisons (and the kleshas generally) came to be seen as the very roots of samsaric existence.

In the Pali Canon's discourses (sutta), kilesa is often associated with the various passions that defile bodily and mental states. In the Pali Canon's Abhidhamma and post-canonical Pali literature, ten defilements are identified, the first three of which – greed, hate, delusion – are considered to be the "roots" of suffering.

In the Pali Canon's Sutta Pitaka, kilesa and its correlate upakkilesa[1] are affective obstacles to the pursuit of direct knowledge (abhiñña) and wisdom (pañña).

For instance, the Samyutta Nikaya includes a collection of ten discourses (SN 27, Kilesa-saṃyutta) that state that any association of "desire-passion" (chanda-rāgo) with the body or mind[2] is a "defilement of mind" (cittasse'so upakkileso):

"Monks, any desire-passion with regard to the eye is a defilement of the mind. Any desire-passion with regard to the ear... the nose... the tongue... the body... the intellect is a defilement of the mind. When, with regard to these six bases, the defilements of awareness are abandoned, then the mind is inclined to renunciation. The mind fostered by renunciation feels malleable for the direct knowing of those qualities worth realizing."[3]

More broadly, the five hindrances – sensual desire (kāmacchanda), anger (byāpāda), sloth-torpor (thīna-middha), restlessness-worry (uddhacca-kukkucca), and doubt (vicikicchā) – are frequently associated with kilesa in the following (or a similar) manner:

[A]ll those Blessed Ones had first abandoned the five hindrances,
defilements of the mind that weaken wisdom ....[4]

While the Sutta Pitaka does not offer a list of kilesa, the Abhidhamma Pitaka's Dhammasangani (Dhs. 1229ff.) and Vibhanga (Vbh. XII) as well as in the post-canonical Visuddhimagga (Vsm. XXII 49, 65) enumerate ten defilements (dasa kilesa-vatthūni) as follows:

The Vibhanga also includes an eightfold list (aṭṭha kilesa-vatthūni) composed of the first eight of the above ten.[8]

Throughout Pali literature, the first three kilesa in the above tenfold Abhidhamma list (lobha dosa moha) are known as the "unwholesome roots" (akusala-mūla or the root of akusal); and, their opposites (alobha adosa amoha) are the three "wholesome roots" (kusala-mūla or the root of kusal).[9] The presence of such a wholesome or unwholesome root during a mental, verbal or bodily action conditions future states of consciousness and associated mental factors (see Karma).[10]

In the 5th-century CE commentarialVisuddhimagga, in its discussion of "Dependent Origination" (Pali: paticca-samuppada) (Vsm. XVII), it presents different expository methods for understanding this teaching's twelve factors (nidana). One method (Vsm. XVII, 298) divides the twelve factors into three "rounds" (vaṭṭa):

So this Wheel of Becoming, having a triple round with these three rounds, should be understood to spin, revolving again and again, forever; for the conditions are not cut off as long as the round of defilements is not cut off.[12]

As can be seen, in this framework, the round of defilements consists of:

Elsewhere in the Visuddhimagga (Vsm. XXII, 88), in the context of the four noble persons (ariya-puggala, see Four stages of enlightenment), the text refers to a precursor to the attainment of nibbana as being the complete eradication of "the defilements that are the root of the round" (vaṭṭa-mūla-kilesā).[14]

The three kleshas of ignorance, attachment and aversion are referred to as the three poisons (Skt. triviṣa) in the Mahayana tradition and as the three unwholesome roots (Pāli, akusala-mūla; Skt. akuśala-mūla ) in the Therevada tradition. These three poisons (or unwholesome roots) are considered to be the root of all the other kleshas.

The Mahayana Mahaparinirvana Sutra lists approximately 50 kleshas, including those of attachment, aversion, stupidity, jealousy, pride, heedlessness, haughtiness, ill-will, quarrelsomeness, wrong livelihood, deceit, consorting with immoral friends, attachment to pleasure, to sleep, to eating, and to yawning; delighting in excessive talking and uttering lies, as well as thoughts of harm.

In general, any defilement or emotion which obscures the mind. They are often summarized as three: ignorance, attachment and aversion. All other negative predispositions are produced on the basis of these three.

Mental factors that produce states of mental torment both immediately and in the long term. The five principal kleshas, which are sometimes called poisons, are attachment, aversion, ignorance, pride, and jealousy.

In Tibetan a mental affliction is defined as a mental process that has the function of disrupting the equilibrium of the mind. They all have that in common, whether or not there is a strong emotional component to it.

Fundamentally, a destructive emotion—which is also referred to as an ‘obscuring’ or ‘afflictive’ mental factor—is something that prevents the mind from ascertaining reality as it is. With a destructive emotion, there will always be a gap between the way things appear and the ways things are.

These are unskilful factors such as greed, hate, delusion, opinionatedness and lack of moral concern. Whereas the term ‘hindrance’ refers to five sticking points, ‘defilement’ is often used without any definite list, but to refer to any function of the mind which is led by unskilful factors.

Kleshas are properties that dull the mind and are the basis for all unwholesome actions. The three main kleshas are passion, aggression, and ignorance.

Chögyam Trungpa. The Truth of Suffering and the Path of Liberation. Edited by Judy L. Lief. Shambhala. p. 134 (from the glossary)

Kleshas

The basic idea is that certain powerful reactions have the capacity to take hold of us and drive our behavior. We believe in these reactions more than we believe in anything else, and they become the means by which we both hide from ourselves and attempt to cope with a world of ceaseless change and unpredictability. The three poisons of greed, hatred, and ignorance are the classic Buddhist examples, but others include conceit, skeptical doubt, and so-called "speculative" views...

The emotional obscurations (in contrast to intellectual obscurations), usually translated as "poisons" or "defilements." The three main klesas are ignorance, hatred, and desire. The five klesas include these three along with pride and envy.

All Buddhist schools teach that through Tranquility (Samatha) meditation the kilesas are pacified, though not eradicated, and through Insight (Vipassana) the true nature of the kilesas and the mind itself is understood. When the empty nature of the Self and the Mind is fully understood, there is no longer a root for the disturbing emotions to be attached to, and the disturbing emotions lose their power to distract the mind.

^Beyond the etymological relationship between and semantic closeness of kilesa and upakkilesa (e.g., see Rhys Davids & Stede, 1921-25, p. 139, entry for upakkilesa at http://dsal.uchicago.edu/cgi-bin/philologic/getobject.pl?c.0:1:3657.pali), the below-referenced Samyutta Nikaya collection entitled "Kilesa-saṃyutta" (SN 27) does not use kilesa in its actual suttas but, in fact, upakkilesa. Bodhi (2000), pp. 1012-14, 1100 n. 273, specifically makes note of the lexical differences between these two Pali words and chooses to translate kilesa as "defilement" and upakkilesa as "corruption." Similar, in Bodhi (2000), p. 1642, SN 47.12, upakkilesa is translated as "corruption" whereas, as indicated below, in Bodhi (2005), p. 416, this same Pali word in the same sutta is translated as "defilement." Consistent with Bodhi (2005), as seen below, Thanissaro (1994) also translates upakkilesa as "defilement."

The related correlate sankilesa (or saṅkilesa) is also translated as "defilement" by Bodhi (e.g., 2000, pp. 903-4; 2005, pp. 55-6), Thanissaro (2004) and Rhys Davids & Stede (1921-5, entry for "Sankilesa"). In SN 22.60 (Bodhi, 2000, pp. 903-4), sankilesa is contextualized by: "By being enamoured with [form], [beings] are captivated by it, and by being captivated by it they are defiled." In this sutta, sankilesa is juxtaposed with purification (visuddhi) which is contextualized by: "Experiencing revulsion [in the impermanence of form's pleasure], [beings] become dispassionate, and through dispassion they are purified."

^In addition to frequent reference in the Abhidhamma and post-canonical Pali literature, references to the unwholesome roots (akusala-mūla) are sprinkled throughout the Sutta Pitaka. For instance, in the Digha Nikaya, it can be found in DN 33 (D iii.215) and DN 34 (D iii.275); in the Majjhima Nikaya, it is the first of several topics discussed by Ven. Sariputta in the well-known Sammādiṭṭhi Sutta ("Right View Discourse," MN 9); and, in the Itivuttaka, a brief discourse on three unwholesome roots starts off the "Section of the Threes" (Iti. 50). However, in none of these Sutta Pitaka texts are the three unwholesome roots referred to as kilesa. Such an association appears to begin in the Abhidhamma texts.

^ abStrictly speaking, in this framework the Visuddhimagga (Vsm. XVII, 298) does not explicitly identify "birth" (jāti) and "aging-death" (jarāmaraṇa) with results (vipāka). Nonetheless, in the preceding paragraph (Vsm. XVII, 297), Buddhaghosa writes: "And in the future fivefold fruit: the five beginning with consciousness. These are expressed by the term 'birth'. But 'ageing-and-death' is the ageing and the death of these [five] themselves" (Ñāṇamoli, 1991, p. 599, v. 297; square-brackets in original). Thus, "birth" and "ageing and death" become correlates or expressions of the five-fold "results" sequence.